There are some name references from Shakespearean plays: Cassie Dorcas (Dorcas, a shepherdess in 'The Winter's Tale'), Jessica (Shylock's daughter in 'The Merchant of Venice'), Isabella Duke (Isabella in 'Measure for Measure')
There are many quotations from 'Hamlet': 'Everlasting had not fixed. His canon 'gainst self-slaughter ..." from Act I Scene 2; 'O That this too solid flesh would melt' from Act I Scene 2; 'Though this be madness, yet there is method in 't.' from Act II Scene 2 ; 'To die, to sleep, to sleep, perchance to dream ..." from Act III Scene 1 ; 'Good night, sweet prince,. And flights of angels sing thee to thy rest!' from Act V Scene 2 ; 'something is rotten in the state of Denmark.' From Act I Scene 4.
The title, "Teach me, dear creature" comes from 'The Comedy of Errors': Act III Scene 2.
"Sound trumpets! - let our bloody colours wave; / And either victory or else a grave ..." comes from 'Henry VI, Part 3: Act II Scene 2.
"Come not between the dragon and his/her wrath" comes from 'King Lear', Act I Scene 1.